In a dramatic shift of sentiment, nearly half of California's likely voters now want to legalize marijuana use in the state, according to a new Field Poll.

"The numbers have flipped (on Proposition 19) since our July poll," said Mark DiCamillo, the poll's director. "That's a major change in the direction of public feelings on legalizing marijuana."

The survey results being released today are especially meaningful since the first ballots for the Nov. 2 election will be cast in a little more than a week from now, starting Oct. 4.

The poll also found that voters remain strongly opposed to Proposition 23, which would suspend AB32, the state law limiting greenhouse gas emissions. Proposition 25, which would end the two-thirds requirement to pass a state budget, holds a solid lead, but the race appears to be rapidly tightening.

But it's California's effort to become the first state in the nation to legalize the sale and use of recreational marijuana for adults 21 and older that's being watched across the country.

Forty-nine percent of those likely voters now support Prop. 19, with 42 percent opposed. In a July poll, 48 percent of those surveyed planned to vote against the ballot initiative, with 44 percent backing legalization.

The reversal came despite a total absence of paid advertising for either side. Neither supporters nor opponents of the measure have raised much money for the Prop. 19 campaign, so far relying on word-of-mouth and media coverage to get their stories out.

That hasn't kept California voters from paying attention to the race, however. The poll found that 84 percent had seen or heard about the effort to legalize marijuana. By contrast, fewer than 40 percent of the voters had heard anything about the other two ballot measures in the survey.

Nine percent of voters are undecided on Prop. 19, which DiCamillo said isn't much of a surprise.

"Everyone knows about it, and it isn't that complicated an issue," he added.

For supporters, the bump in the numbers shows that their message is getting through.

"Police, sheriffs and judges have been speaking out recently in support of Prop. 19's commonsense solution to control and tax marijuana like alcohol and tobacco - to allow police to focus on violent crime," said Dan Newman, a spokesman for the Yes on 19 campaign.

Opponents of the measure, who include a number of law-enforcement figures, are confident the numbers will change.

"Obviously, this is a volatile electorate, but that doesn't change the fact that no poll has shown (legalization supporters) with the 50 percent they need to win," said Roger Salazar, a spokesman for the No on 19 effort.

In 1996, California voters legalized the use of medical marijuana, passing Prop. 215 with nearly 56 percent of the vote. A 1972 effort to legalize marijuana in the state, also Prop. 19, was steamrolled, collecting only a third of the votes.

More than 40 years of polling by Field shows just how dramatic the shift on marijuana has been. In 1969, just 13 percent of California adults wanted to legalize marijuana, while 49 percent called on the state to pass new, tougher laws against the drug.

By 1983, 30 percent of registered voters favored legalization, but 32 percent still wanted to crack down on users.

Now close to 50 percent of registered voters want marijuana legalized and only 14 percent want harsher laws.

Men and women have very different views of Prop. 19, as do the young and the old. While 54 percent of men back legalization, only 44 percent of women support Prop. 19. Nearly 60 percent of the youngest voters, those under 40, want to see marijuana made legal. Fifty-three percent of those 65 and older oppose it.

"With a lot of people considering and reconsidering ... this is probably not as solid a 49 percent (support) as can be," DiCamillo said. "Turnout matters a great deal, and if the young voters don't turn out, it could make a big difference."

Support for Prop. 19 also breaks along geographic and political lines, with the heavily Democrat coastal counties 54 percent in favor while the more Republican inland areas are 52 percent opposed. Not surprisingly, the measure's strongest support comes from the Bay Area and Los Angeles County, where just under 60 percent favor legalization.

More than 60 percent of Democrats and decline-to-state voters plan to vote for Prop. 19.

A Field survey taken in July found that 60 percent of Bay Area registered voters said they had used marijuana, far above the 47 percent state average. Slightly more than half the state's men reported using the drug, compared with 43 percent of women.

The poll found little movement surrounding Prop. 23, even though it's becoming a major battleground in the races for governor and U.S. Senate. While the 45 percent who oppose suspending the greenhouse gas rules dropped from July's 48 percent, support for the initiative also slipped from 36 percent in July to 34 percent in the newest poll. More than a fifth of voters now are undecided.

Support for the Democrat-backed Prop. 25 has skidded dramatically since July, when it was supported by 65 percent of the voters. The new poll has proponents of the measure with a 46 to 30 percent lead, but more tightening is likely, DiCamillo said.

The July poll had 58 percent of Republicans supporting the change, which party leaders argue will allow Democrats to pass a state budget without any GOP votes. In the new poll, Republican support has dropped to 30 percent, with another 30 percent undecided.

"This is a measure that is still in flux, and you can't really tell where it will end up," DiCamillo said. "Republican voters are in transition ... as they try to decide who the winners and losers will be."

The poll is based on a telephone survey taken from Sept. 14-21 of 857 registered voters, including 599 identified as likely to vote in November. The margin of error based on the sample is plus or minus 4.1 percentage points.